Multiple choice

The ratio of the ages of A : B seven years ago was (3 : 4) respectively. The ratio of their ages 9 years from now will be (7 : 8) respectively. What is B's age at present?

  1. 29 years

  2. 32 years

  3. 33 years

  4. 23 years

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let A's and B's present ages be 3x+7 and 4x+7. After 9 years: (3x+16)/(4x+16) = 7/8. Cross-multiply: 8(3x+16) = 7(4x+16). 24x+128 = 28x+112. 16 = 4x, so x = 4. B's present age = 4(4)+7 = 23 years. Option D (23 years) is correct. Options A, B, C give 29, 32, 33 which don't satisfy the ratio conditions.

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